Takano S, Tuda M, Takasu K, Furuya N, Imamura Y, Kim S, Tashiro K, Iiyama K, Tavares M, Amaral AC, Unique clade of alphaproteobacterial endosymbionts induces complete cytoplasmic incompatibility in the coconut beetle., Proceedings of the National Academy of Sciences of the United States of America (PNAS), 10.1073/pnas.1618094114, 114(23), 6110–6115, 2017.06, Maternally inherited bacterial endosymbionts in arthropods manipulate host reproduction to increase the fitness of infected females. Cytoplasmic incompatibility (CI) is one such manipulation, in which uninfected females produce few or no offspring when they mate with infected males. To date, two bacterial endosymbionts, Wolbachia and Cardinium, have been reported as CI inducers. Only Wolbachia induces complete CI, which causes 100% offspring mortality in incompatible crosses. Here we report a third CI inducer that belongs to a unique clade of Alphaproteobacteria detected within the coconut beetle, Brontispa longissima. This beetle comprises two cryptic species, the Asian clade and the Pacific clade, which show incompatibility in hybrid crosses. Different bacterial endosymbionts, a unique clade of Alphaproteobacteria in the Pacific clade and Wolbachia in the Asian clade, induced bidirectional CI between hosts. The former induced complete CI (100% mortality), whereas the latter induced partial CI (70% mortality). Illumina MiSeq sequencing and denaturing gradient gel electrophoresis patterns showed that the predominant bacterium detected in the Pacific clade of B. longissima was this unique clade of Alphaproteobacteria alone, indicating that this endosymbiont was responsible for the complete CI. Sex distortion did not occur in any of the tested crosses.The 1,160 bp of 16S rRNA gene sequence obtained for this endosymbiont had only 89.3% identity with that of Wolbachia, indicating that it can be recognized as a distinct species. We discuss the potential use of this bacterium as a biological control agent..

4.

Kébé K, Alvarez N, Tuda M, Arnqvist G, Fox CW, Sembène M, Espíndola A, Global phylogeography of the insect pest Callosobruchus maculatus (Coleoptera: Bruchinae) relates to the history of its main host, Vigna unguiculata., Journal of Biogeography 44, 2515–2526, in press, 2017.11, Aim: The seed beetle Callosobruchus maculatus is an important tropical and subtropical pest of legumes distributed world-wide. Archaeological evidence suggests an African origin with later world-wide invasion facilitated by the last centuries’ legume trading and exchange. To date, no studies could identify the routes or timing of dispersal of the species. Here, we investigate the global phylogeography of this pest to shed light on the main inter-continental dispersal routes that led to it becoming a cosmopolitan pest.Location: World-wide.Methods: We sampled seed beetles over a large fraction of the species’ range and sequenced one nuclear and three mitochondrial loci. Using this data, we estimated spatio-temporal phylogeographical reconstructions, and the demographic history of the species. We also used our dataset to evaluate the effect of panmixia on Bayesian demographic estimations.Results: Callosobruchus maculatus exhibited regional and continental genetic structure, with the highest genetic diversity found in Africa. Our discrete Bayesian phylogeographical approach indicated that the species first dispersed to Asia and then colonized the pantropical belt. The three methods used for inferring the demographic history of C. maculatus indicated a recent demographic expansion in the world-wide dataset, as well as in the subset restricted to African samples. Such a signal was, however, not observed in the subset composed of Asian specimens. This demographic expansion occurred in the Holocene and is likely explained by the spread of cowpea and other host legumes across and out of Africa. Main conclusions: The inferred dispersal routes support the idea that the evolutionary history of C. maculatus relates to the trade of its main host plant, Vigna unguiculata. Human-mediated processes appear to have shaped the global genetic structure of this pest. As a methodological implication, we demonstrate that coalescent-based demographic reconstructions can be erroneous if the dataset violates the assumption of panmixia..

Saeki Y, Tani S, Fukuda K, Iwase S, Sugawara Y, Tuda M, Takagi M, Costs and benefits of larval jumping behaviour of Bathyplectes anurus., The Science of Nature, 10.1007/s00114-015-1324-1, 103, 1, 2016.02, Bathyplectes anurus, a parasitoid of the alfalfa weevils, forms a cocoon in the late larval stage and exhibits jumping behaviour. Adaptive significance and costs of the cocoon jumping have not been thoroughly studied. We hypothesised that jumping has the fitness benefits of enabling habitat selection by avoiding unfavourable environments. We conducted laboratory experiments, which demonstrated that jumping frequencies increased in the presence of light, with greater magnitudes of temperature increase and at lower relative humidity. In addition, when B. anurus individuals were allowed to freely jump in an arena with a light gradient, more cocoons were found in the shady area, suggesting microhabitat selection. In a field experiment, mortality of cocoons placed in the sun was significantly higher than for cocoons placed in the shade. B. anurus cocoons respond to environmental stress by jumping, resulting in habitat selection. In the presence of potential predators (ants), jumping frequencies were higher than in the control (no ant) arenas, though jumping frequencies decreased after direct contact with the predators. Body mass of B. anurus cocoons induced to jumpsignificantly decreased over time than cocoons that did not jump, suggesting a cost to jumping. We discuss the benefits and costs of jumping behaviour and potential evolutionary advantages of this peculiar trait, which is present in a limited number of species..

7.

Iwase S, Tani S, Saeki Y, Tuda M, Haran J, Skuhrovec J, Takagi M, Dynamics of infection with Wolbachia in Hypera postica (Coleoptera: Curculionidae) during invasion and establishment., Biological Invasions, 17, 12, 3639-3648, 2015.12, The process of loss or gain of parasites during invasion of new lands is not well understood. The alfalfa weevil Hypera postica is an invasive pest of various leguminous crops and consists of three major mitochondrial haplotypes, ‘Western’, ‘Egyptian’ and ‘Eastern’. The Western strain is infected with the endosymbiotic proteobacteria Wolbachia, that cause unidirectional complete reproductive incompatibility, in its native (Europe) and an introduced (the United States) ranges. However, our preliminary screening of a few introduced populations in Northern Kyushu, southwestern Japan, failed to detect Wolbachia from the Western strain. A larger-scale and historical assessment of Wolbachia infection may allow to estimate when and how the bacteria were lost, and current geographical distribution of infection among host haplotypes. In this study, we aim to assess the Wolbachia-infection status of H. postica populations throughout Northern Kyushu, where H. postica invasion to Japan was first found. A total of 228 individuals from seven regions in Northern Kyushu collected in different time periods from 1982 to 2015 and 14 individuals from Europe were subjected to PCR diagnostics for Wolbachia. Wolbachia from the Western strain was not detected, irrespective of the time periods and geographic areas in Northern Kyushu. We found ‘Egyptian’-strain H. postica collected most recently from an island off Kyushu harboured a supergroup-B Wolbachia variant. This variant was genetically different from the European Wolbachia variant infecting Western-strain H. postica. The infection was new to the Egyptian haplotype and was estimated to have taken place independently of the loss in the Western strain..

Arnqvist G, Sayadi A, Immonen E, Hotzy C, Rankin D, Tuda M, Hjelmen CE, Johnston JS, Genome size correlates with reproductive fitness in seed beetles., Proceedings of the Royal Society B, 282 (1815), 20151421, 2015.09, The ultimate cause of genome size (GS) evolution in eukaryotes remains a major and unresolved puzzle in evolutionary biology. Large-scale comparative studies have failed to find consistent correlations between GS and organismal properties, resulting in the ‘C-value paradox’. Current hypotheses for the evolution of GS are based either on the balance between mutational events and drift or on natural selection acting upon standing genetic variation in GS. It is, however, currently very difficult to evaluate the role of selection because within-species studies that relate variation in lifehistory traits to variation in GS are very rare. Here, we report phylogenetic comparative analyses of GS evolution in seed beetles at two distinct taxonomic scales, which combines replicated estimation of GS with experimental assays of life-history traits and reproductive fitness. GS showed rapid and bidirectional evolution across species, but did not show correlated evolution with any of several indices of the relative importance of genetic drift. Within a single species, GS varied by 4–5% across populations and showed positive correlated evolution with independent estimates of male and female reproductive fitness. Collectively, the phylogenetic pattern of GS diversification across and within species in conjunction with the pattern of correlated evolution between GS and fitness provide novel support for the tenet that natural selection plays a key role in shaping GS evolution..

Tuda M, Kagoshima K, Toquenaga Y, Arnqvist G, Global genetic differentiation in a cosmopolitan pest of stored beans: effects of geography, host-plant usage and anthropogenic factors., PLoS ONE, 10.1371/journal.pone.0106268, 9, 9, e106268, 2014.09, Genetic differentiation can be promoted allopatrically by geographic isolation of populations due to limited dispersal ability and diversification over time or sympatrically through, for example, host-race formation. In crop pests, the trading of crops across the world can lead to intermixing of genetically distinct pest populations. However, our understanding of the importance of allopatric and sympatric genetic differentiation in the face of anthropogenic genetic intermixing is limited. Here, we examined global sequence variation in two mitochondrial and one nuclear genes in the seed beetle Callosobruchus maculatus that uses different legumes as hosts. We analyzed 180 samples from 42 populations of this stored bean pest from tropical and subtropical continents and archipelagos: Africa, the Middle East, South and Southeast Asia, Oceania and South America. For the mitochondrial genes, there was weak but significant genetic differentiation across continents/archipelagos. Further, we found pronounced differentiation among subregions within continents/archipelagos both globally and within Africa but not within Asia. We suggest that multiple introductions into Asia and subsequent intermixing within Asia have generated this pattern. The isolation by distance hypothesis was supported globally (with or without continents controlled) but not when host species was restricted to cowpeas Vigna unguiculata, the ancestral host of C. maculatus. We also document significant among-host differentiation both globally and within Asia, but not within Africa. We failed to reject a scenario of a constant population size in the recent past combined with selective neutrality for the mitochondrial genes. We conclude that mitochondrial DNA differentiation is primarily due to geographic isolation within Africa and to multiple invasions by different alleles, followed by host shifts, within Asia. The weak inter-continental differentiation is most likely due to frequent inter-continental gene flow mediated by human crop trade..

Arnqvist, G., Dowling, D.K., Eady, P., Gay, L., Tregenza, T., Tuda, M. and Hosken, D.J., The genetic architecture of metabolic rate: environment specific epistasis between mitochondrial and nuclear genes in an insect., Evolution, 64, 3354-3363, 2010.12, 近年、ミトコンドリア（mt）DNAが、エネルギー生産する酵素複合体を一緒に作る核遺伝子と共進化することが解明されている。これはmt遺伝子と核遺伝子の間のゲノム間エピスタシスが生物個体全体の代謝表現型に影響することを示唆する。そこでヨツモンマメゾウムシの複数のmt系統と核系統間で組み合わせ交配し、代謝率を2つの異なる温度下で測定した。代謝率はmtと核の系統間交互作用と温度に影響された。塩基配列データは、mtの遺伝的変異がこの交互作用の結果を決めることを示唆した。この実験は、２つのゲノムの遺伝的相互作用と遺伝子型x遺伝子型x環境間交互作用を明らかにした。これらの結果は1. 生活史進化一般、特に温度適応の複雑性に洞察を与え、2. 非中立的なmtDNA多型の維持機構を示唆する。The extent to which mitochondrial DNA (mtDNA) variation is involved in adaptive evolutionary change is currently being reevaluated. In particular, emerging evidence suggests that mtDNA genes coevolve with the nuclear genes with which they interact to form the energy producing enzyme complexes in the mitochondria. This suggests that intergenomic epistasis between mitochondrial and nuclear genes may affect whole-organism metabolic phenotypes. Here, we use crossed combinations of mitochondrial and nuclear lineages of the seed beetle Callosobruchus maculatus and assay metabolic rate under two different temperature regimes. Metabolic rate was affected by an interaction between the mitochondrial and nuclear lineages and the temperature regime. Sequence data suggests that mitochondrial genetic variation has a role in determining the outcome of this interaction. Our genetic dissection of metabolic rate reveals a high level of complexity, encompassing genetic interactions over two genomes, and genotype x genotype x environment interactions. The evolutionary implications of these results are twofold. First, because metabolic rate is at the root of life histories, our results provide insights into the complexity of life-history evolution in general, and thermal adaptation in particular. Second, our results suggest a mechanism that could contribute to the maintenance of nonneutral mtDNA polymorphism..

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Arnqvist, G., Tuda, M., Sexual conflict and the gender load: correlated evolution between population fitness and sexual dimorphism in seed beetles., Proceedings of the Royal Society B, 277, 1345-1352, 2010.04, 雌雄はゲノムの大半を共有しながらも選択は異なる。性的対立する遺伝子座は理論上、集団内の性的負荷を引き起こす。しかし、遺伝子座内性的対立(ISC)が移行的な進化的状態（性的二型（SD）の進化により対立は急速に解消）なのか、慢性的な適応障害なのか、は現在明らかでない。同じ条件下では、ISCは雌雄において表現される形質の集団適応度とSDの相関進化として現れるはずだ。そこで同じ飼育環境に適応したマメゾウムシの異なる実験室集団間で適応度とSDを比較しISCの効果を試験した。重要な生活史形質である幼生発育期間のSDは適応度と正の関係があり、これは集団適応度と発育期間の相関進化（雌で正、雄で負）によった。雌雄間の遺伝的結合を緩めることで雌雄がそれぞれの異なる適応度ピークへと近づいたと言える。Although males and females share much of the same genome, selection is often distinct in the two sexes. Sexually antagonistic loci will in theory cause a gender load in populations, because sex-specific selection on a given trait in one sex will compromise the adaptive evolution of the same trait in the other sex. However, it is currently not clear whether such intralocus sexual conflict (ISC) represents a transient evolutionary state, where conflict is rapidly resolved by the evolution of sexual dimorphism (SD), or whether it is a more chronic impediment to adaptation. All else being equal, ISC should manifest itself as correlated evolution between population fitness and SD in traits expressed in both sexes. However, comparative tests of this prediction are problematic and have been unfeasible. Here, we assess the effects of ISC by comparing fitness and SD across distinct laboratory populations of seed beetles that should be well adapted to a shared environment. We show that SD in juvenile development time, a key life-history trait with a history of sexually antagonistic selection in this model system, is positively related to fitness. This effect is due to a correlated evolution between population fitness and development time that is positive in females but negative in males. Loosening the genetic bind between the sexes has evidently allowed the sexes to approach their distinct adaptive peaks..

28.

Yanagi S, Tuda M, Interaction effect among maternal environment, maternal investment and progeny genotype on life history traits in Callosobruchus chinensis., Functional Ecology, 24, 2, 383-391, 2010.04, 母親の環境条件（前世代の環境preE）に依存して、母親から子への投資量（環境E）が変化するとき、適応度を上げるために子の遺伝子（G）の発現も変化すると予測される。アズキゾウムシにおいて、EとGの遺伝相関の影響を取り除くために近交系の雌を用いて、preEとEに対するGの反応を調べた。高密度（preE）飼育した母親との交配では低密度適応した野外系統の父親の子（G）が、低密度（preE）飼育した母親とでは高密度適応した室内系統の父親の子（G）が、卵サイズ（E）の増大とともに発育期間が急激に短くなり（適応度が上がり）予測を支持した。このような密度依存的な母性効果（preE×E×G交互作用）は、新しい環境における急速な適応進化を可能にする。1. Transgenerational effects, genetic or non-genetic, affect population dynamics and the evolution of life-history traits. Besides genetic components, the size of gametes (eggs and seeds), simultaneously a parental and progeny character, can mediate environmental condition experienced by a parent. In both animals and arthropods, mothers are known to reduce their egg mass depending on their malcondition. 2. Progeny may also modify their life history traits to increase their own fitness when constrained by maternal investment, which may eventually nullify transgenerational effects on population dynamics and evolution. Such fitness modification by the progeny under new environmental conditions requires phenotypic plasticity interacting with egg mass. We hypothesize that different selective environments should produce inter-population genetic diversification of the response to maternal investment on each egg, which would be detected as a paternal genotype x environment x previous (i.e. maternal) environment (G x E x preE) interaction in progeny fitness. 3. To evaluate the contribution of maternal non-genetic resource and the genetic component separately, we used an inbred-isofemale-line approach to eliminate the influence of the genetic correlation between egg mass and other life history traits, in the adzuki bean beetle, Callosobruchus chinensis. The females were reared at either high or low densities to generate variability in egg resources. To test the additive or interactive effect of genotype, non-genetic egg resources, and maternal environment on the life history traits of the progeny, they were crossed with males from laboratory and wild strains that had been subjected to different levels of population density. 4. The G x E x preE interaction effect was detected on the correlation structure between egg mass and development time: In the offspring of mothers reared at low density, the negative correlation between egg mass and development time was higher with lab strain fathers, whereas in the offspring of mothers reared at high density, the negative correlation was higher with the wild strain fathers. 5. Our results indicate a genetic difference in the response of development time but not of adult mass to environmental variation in egg mass. Such density-dependent enhancement of maternal effects may destabilize population dynamics and accelerate evolution..

Luna Maldonado, A.I., Yamaguchi, Y., Tuda, M. and Nakaji, K., Development of an intelligent robot for an agricultural production ecosystem (III) - modeling of the predation of rice plants and weeds by golden apple snail –., Journal of the Faculty of Agriculture, Kyushu University, 53(2), 517-521, 2008.12.

33.

Luna Maldonado, A.I., Yamaguchi, Y., Tuda, M. and Nakaji, K., Development of an intelligent robot for an agricultural production ecosystem (II) - modeling of the competition between rice plants and weeds -., Journal of the Faculty of Agriculture, Kyushu University, 53(2), 511-516, 2008.12.

34.

Tuda M, A new species of Bruchidius (Coleoptera: Chrysomelidae: Bruchinae) from Albizia in Northern Thailand and a review of Bruchidius Group 5., Zoological Science, 25(4), 451-454, 2008.04.